Men and women sometimes eat food that doesn't agree with them. Either because it is too rich, or they have eaten too much. This gives them uncontrollable wind, and ultiamtely a severe dose of the shits', which can cause considerable embarrassment. Dropping your bat literally means you have had something hanging from your drainpipe, which has been festering away and fucking stinks.

Rupert, "I say old chap, did you drop your bat?"

Ciril: "heavens man what do you mean by that terminology,please explain yourself?"

Rupert "Well the fuckingstench is unbearble old bean, it appears you have something hanging from your arse."